Distributed Database Management Systems: Lecture 9. The main topics covered in this chapter include: networks continued, DDBMS architecture; local area network; metropolitan area network; wide area network; maintained during conversation;...
Distributed Database Management Systems Lecture 09 In the previous lecture • Derived Relational Algebra Ops… • Relational Calculus • Computer Networks In this Lecture • Networks continued • DDBMS Architecture Scale • Local Area Network • Metropolitan Area Network • Wide Area Network WANs • Used Inter-City, country or even continental • Gives low bandwidth, high latency • Can be Broadcast and Point to Point • In Point to Point –Circuit Switching –Packet Switching Circuit Switching • Dedicated link b/w Sender Receiver • Maintained during conversation Packet Switching • Message into Packets • May take different routes • Need to be sorted Advantages of Packet Switching • Better Link Utilization • Bursty Nature of communication • Parallel transmission Protocol Standards Set of rules and formats for exchanging data, arranged into layers called protocol suite/ stack • WAN faces max heterogeneity • Needs protocols • ISO/OSI ISO/OSI Architecture • Network built in seven layers • Interfaces for passing information b/w layers • Protocols between corresponding layers at different sites • Lower three layers form Comm subnet TCP/IP Architecture • Another popular Architecture • Five layers • IEEE Committee 802 Distributed DBMS Architecture Architecture of a systems defines its structure Sheth, A P., Larson, J A., ‘ Federated Database Systems for Managing Distributed Heterogeneous, and Autonomous Databases’, ACM Computing Surveys, 22, No 3, p(183-236), Sep., 90 • Three major (idealized) architectures of DDBMS discussed –Peer to peer –Client/Server –Multidatabase DBMS Standardization A conceptual framework to divide standardization work into manageable pieces • Component-based • Function-based • Data-based Practically • Every aspect has to be considered • These Classification schemes are Orthogonal • A committee for the task established in 1972 by ANSI under SPARC • Published standard in 1977 Reference Model Users External Schema External View Conceptual Schema Internal Schema External View Conceptual View Internal View External View ... 802 Distributed DBMS Architecture Architecture of a systems defines its structure Sheth, A P., Larson, J A., ‘ Federated Database Systems for Managing Distributed Heterogeneous, and Autonomous Databases’,...In the previous lecture • Derived Relational Algebra Ops… • Relational Calculus • Computer Networks In this Lecture • Networks continued • DDBMS Architecture... Computing Surveys, 22, No 3, p(183-236), Sep., 90 • Three major (idealized) architectures of DDBMS discussed –Peer to peer –Client/Server –Multidatabase DBMS Standardization A conceptual framework